Partition plate

ABSTRACT

A partition plate is configured to separate an intake passage formed by an intake pipe to be coupled to a combustion chamber into a first intake passage and a second intake passage. The first intake passage is openable and closable by a valve. A shape of a first cross section orthogonal to an extending direction of the intake pipe is set on the basis of a shape of a surface of the intake pipe that faces the partition plate with the second intake passage interposed therebetween.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent ApplicationNo. 2017-063933 filed on Mar. 28, 2017, the entire contents of which arehereby incorporated by reference.

BACKGROUND 1. Technical Field

The present invention relates to partition plates disposed inside intakepipes.

2. Related Art

In the related art, an engine is provided with a partition plate thatpartitions an intake passage within an intake pipe into two intakepassages (a first intake passage and a second intake passage) so as togenerate a tumble flow (vertical vortex) within a combustion chamber.When the load is small and the intake flow rate is low, for instance,the opening of the first intake passage partitioned by the partitionplate is reduced by a tumble generation valve (TGV) so as to increasethe flow speed of intake air flowing into the combustion chamber fromthe second intake passage, whereby a strong tumble flow can be generatedwithin the combustion chamber.

In the disclosure of Japanese Unexamined Patent Application Publication(JP-A) No. 2010-090849, two intake ports branching off from an intakemanifold substantially have an isosceles triangle shape in which thesurface where the two intake ports face each other serves as the base,so that a stronger tumble flow can be effectively generated.

However, in the related-art technology described in JP-A No.2010-090849, the direction of the circulation axis of the generatedtumble flow is inconsistent at a plurality of positions in the directionorthogonal to the direction extending from the intake side toward theexhaust side within the combustion chamber. This causes, for instance, asecondary flow (horizontal vortex) to occur in the swirling directionduring the compression stroke of the engine, which is problematic inthat the air-fuel mixture cannot be stably combusted during thecombustion stroke of the engine.

SUMMARY OF THE INVENTION

It is desirable to provide a partition plate that can effectivelygenerate a tumble flow and that can improve the combustion stability ofan engine.

An aspect of the present invention provides a partition plate configuredto separate an intake passage formed by an intake pipe to be coupled toa combustion chamber into a first intake passage and a second intakepassage. The first intake passage is openable and closable by a valve. Ashape of a first cross section orthogonal to an extending direction ofthe intake pipe is set on the basis of a shape of a surface of theintake pipe that faces the partition plate with the second intakepassage interposed therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates the configuration of an engine;

FIGS. 2A to 2C schematically illustrate the shape of a combustionchamber of the engine;

FIG. 3 is a diagram for explaining the length in the circumferentialdirection relative to the position in the x direction of the combustionchamber;

FIG. 4 is a schematic cross-sectional view of an intake pipe;

FIG. 5 is a schematic cross-sectional view of the intake pipe and apartition plate according to an example; and

FIG. 6 is a schematic cross-sectional view of an intake pipe and apartition plate according to a modification.

DETAILED DESCRIPTION

A preferred example of the present invention will be described in detailbelow with reference to the appended drawings. For instance, thedimensions, materials, and other specific numerical values indicated inthis example are merely examples for providing an easier understandingof the example of the invention and are not intended to limit theexample of the present invention, unless otherwise specified. In thisdescription and the drawings, components having substantially identicalfunctions and configurations are given the same reference signs, andredundant descriptions thereof are omitted. Furthermore, components thatare not directly related to the example of the present invention are notillustrated in the drawings.

FIG. 1 schematically illustrates the configuration of an engine 1. Asillustrated in FIG. 1, the engine 1 is provided with a cylinder block10, a crankcase 12 integrated with the cylinder block 10, and a cylinderhead 14 coupled to the cylinder block 10.

The cylinder block 10 has a plurality of cylinder bores 16. In eachcylinder bore 16, a piston 18 is slidably supported by a connecting rod20. A space surrounded by the inner wall surface of the cylinder head14, the inner wall surface of the cylinder bore 16, and the crown of thepiston 18 serves as a combustion chamber 22.

A crankshaft 26 is rotatably supported within a crank chamber 24 formedby the crankcase 12. The crankshaft 26 is coupled to the piston 18 bythe connecting rod 20. Thus, the piston 18 is coupled to the crankshaft26 by the connecting rod 20.

The cylinder head 14 has an intake port 28 and an exhaust port 30 thatspatially communicate with the combustion chamber 22. The intake port 28has one opening at the intake upstream side and two openings at theintake downstream side facing the combustion chamber 22, and branchesoff into two passages in midstream from the upstream side toward thedownstream side. The head of an intake valve 32 is located between theintake port 28 and the combustion chamber 22. The intake valve 32 opensand closes the intake port 28 relative to the combustion chamber 22 inaccordance with rotation of a camshaft (not illustrated).

An upstream end 14 a where the intake port 28 is provided in the outerwall surface of the cylinder head 14 is coupled to an intake manifold34. An intake passage 36 to which intake air is introduced is providedinside the intake manifold 34 and the intake port 28. The intakemanifold 34 and the intake port 28 that constitute the intake passage 36will collectively be referred to as “intake pipe 60” hereinafter.

The exhaust port 30 has two openings at the exhaust upstream side facingthe combustion chamber 22 and one opening at the exhaust downstreamside, and merges into one passage in midstream from the upstream sidetoward the downstream side. The head of an exhaust valve 38 is locatedbetween the exhaust port 30 and the combustion chamber 22. The exhaustvalve 38 opens and closes the exhaust port 30 relative to the combustionchamber 22 in accordance with rotation of a camshaft (not illustrated).

A downstream end 14 b where the exhaust port 30 is provided in the outerwall surface of the cylinder head 14 is coupled to an exhaust manifold40. An exhaust passage 42 to which exhaust air is introduced is providedinside the exhaust port 30 and the exhaust manifold 40. The exhaustmanifold 40 and the exhaust port 30 that constitute the exhaust passage42 will collectively be referred to as “exhaust pipe 70” hereinafter.

The cylinder head 14 is provided with an injector 44 and an ignitionplug 46, the tips of which are located within the combustion chamber 22.Fuel is sprayed from the injector 44 toward intake air flowing into thecombustion chamber 22 via the intake port 28. By discharging electricityfrom the ignition plug 46 at a predetermined timing, a mixture of theintake air and the fuel is ignited and combusted. The combustion causesthe piston 18 to reciprocate within the cylinder bore 16, and thereciprocation is converted into rotation of the crankshaft 26 via theconnecting rod 20.

The intake passage 36 is provided with a partition plate 48 and a tumblegeneration valve (TGV) 50. The partition plate 48 and the TGV 50 areprovided between a throttle valve (not illustrated) and the combustionchamber 22. In this example, the partition plate 48 is disposed suchthat one end is provided at a predetermined position inside the intakemanifold 34 and the other end is provided at a position in front of(i.e., upstream of) where the passage inside the intake port 28 branchesoff into two passages. Alternatively, this example is not limited tothis configuration, such that the other end may extend to a positionbehind (i.e., downstream of) where the passage inside the intake port 28branches off into two passages. The partition plate 48 extends in theintake-air flowing direction within the intake passage 36 (i.e., theextending direction of the intake pipe 60) and partitions (separates)the intake passage 36 into a first intake passage 36 a and a secondintake passage 36 b. The TGV 50 is disposed at a position facing thefirst intake passage 36 a at the upstream side of the partition plate 48and adjusts the opening of the first intake passage 36 a.

As illustrated in FIG. 1, when the opening of the TGV 50 is at a minimumand one of the passages partitioned by the partition plate 48 (i.e., thefirst intake passage 36 a in this case) is closed by the TGV 50, the airintroduced to the intake passage 36 travels through the other passagepartitioned by the partition plate 48 (i.e., the second intake passage36 b in this case) so as to be introduced to the combustion chamber 22.

In a case where the load is small and the intake flow rate is low in theengine 1, the opening of the TGV 50 is reduced so as to cause most ofthe intake air to travel through the second intake passage 36 bpartitioned by the partition plate 48. Accordingly, in the engine 1, theair with the increased flow speed is made to flow into the combustionchamber 22, so that a strong tumble flow indicated by an arrow isgenerated within the combustion chamber 22. Consequently, the engine 1achieves improved fuel consumption owing to improved fuel dilution andhigher lean-burn limit, as well as improved combustion stability owingto fast combustion.

Alternatively, this example is not limited to this configuration, suchthat the second intake passage 36 b may be closed by the TGV 50 and theintake air may be introduced into the combustion chamber 22 via thefirst intake passage 36 a.

FIGS. 2A to 2C schematically illustrate the shape of the combustionchamber 22. Specifically, FIG. 2A schematically illustrates the shape ofthe combustion chamber 22. In FIG. 2A, the combustion chamber 22 isgiven a cylindrical shape for simplifying the description of the shapeof the combustion chamber 22. Directions extending through a center O ofthe upper surface of the combustion chamber 22 and orthogonal to oneanother are expressed as “x direction”, “y direction”, and “zdirection”. The direction extending from the intake side toward theexhaust side in the cylinder head 14 (i.e., the combustion chamber 22)will be defined as “y direction” (second direction), the axial directionof the cylinder bore 16 will be defined as “z direction” (firstdirection), and the direction orthogonal to the y direction and the zdirection will be defined as “x direction”.

A tumble flow indicated by an empty arrow in FIG. 2A and circulatingwithin a y-z cross section is generated such that a tumble flow with thesame circulation time and the same circulation axis (sometimes referredto as “good tumble flow” hereinafter) is generated at any of a pluralityof different positions on the x axis, thereby suppressing rotation ofthe tumble flow in the direction of the x-y plane (i.e., a directionorthogonal to the axial direction of the cylinder bore 16) during thecompression stroke of the engine 1. By suppressing rotation of thetumble flow in the direction of the x-y plane during the compressionstroke of the engine 1, improved combustion stability can be achieved inthe combustion stroke after the compression stroke. In other words, astable high-dilution high-lean-burn operation of the engine 1 can berealized.

In order to achieve such a good tumble flow in this example, the shapeof the partition plate 48 is set based on the shape of the combustionchamber 22 and the shape of the intake pipe 60.

The method for setting the shape of the partition plate 48 will bedescribed in detail below.

FIG. 2B illustrates a cross-sectional shape a of the combustion chamber22, indicated by a dash line in FIG. 2A, taken through a positionshifted from the center O in the x direction. FIG. 2C illustrates across-sectional shape b of the combustion chamber 22, indicated by asingle-dot chain line in FIG. 2A, taken through a y-z cross sectionextending through the center O.

In this example, the cross-sectional shape a and the cross-sectionalshape b are both rectangular. A length (perimeter) La (x, θ) of each ofthe cross-sectional shape a and the cross-sectional shape b in thecircumferential direction indicated by arrows in FIGS. 2B and 2C iscalculated by using expressions (1) to (3) indicated below, where Bdenotes a cylinder bore diameter (cylinder inner diameter) of the engine1 and H(θ) denotes a stroke that changes in accordance with a crankangle θ of the engine 1. The crank angle θ is set to 0° in a case wherethe piston 18 is located at the top dead center in the intake stroke.x ² +y(x)²=(B/2)²  (1)2y(x)=2√((B/2)² −x ²)  (2)La(x,θ)=2×2y(x)+2×H(θ)  (3)

FIG. 3 is a diagram for explaining the length La(x, θ) in thecircumferential direction relative to the position in the x direction.In FIG. 3, the perimeter La(x, θ) illustrated is calculated by usingexpression (3) in a case where, for instance, the crank angle θ is 300°.Alternatively, the crank angle θ used when calculating the stroke H(θ)in expression (3) is not limited to this value and may be set to anyvalue. When evaluating the perimeter La(x, θ), it is desirable that theevaluation be performed before the tumble flow becomes compressed andcollapsed after the intake valve 32 is closed. Therefore, it isdesirable to set the crank angle θ between 180° and 340°.

As it is apparent from expression (3) and FIG. 3, the perimeter La(x, θ)in the y-z cross section (second cross section) of the combustionchamber 22 changes in accordance with the position in the x direction,assuming that the crank angle θ (stroke) is fixed. For instance, whenthe cross-sectional shape a and the cross-sectional shape b that havethe same crank angle θ (stroke) in FIGS. 2B and 2C are compared, theperimeter La (x=0, θ) of the cross-sectional shape b is larger than theperimeter La (x>0, θ) of the cross-sectional shape a. As illustrated inFIG. 3, the perimeter La (x, θ) is at a maximum when x=0.

Therefore, in order to generate a good tumble flow within such acombustion chamber 22, it is necessary to consider the perimeter La(x,θ) of the y-z cross section of the combustion chamber 22. Specifically,if a tumble flow having a speed (flow speed) according to the perimeterLa(x, θ) is generated, the tumble flow would have the same circulationtime and the same circulation axis in each y-z cross section within thecombustion chamber 22.

For instance, the speed (first flow speed) of the tumble flow generatedin the cross-sectional shape b is set to be higher than the speed(second flow speed) of the tumble flow generated in the cross-sectionalshape a, and the time it takes for the tumble flow to make one fullcircuit in the cross-sectional shape b is set equal to the time it takesfor the tumble flow to make one full circuit in the cross-sectionalshape a. As a result, the circulation time and the circulation axis ofthe tumble flow are made identical between the cross-sectional shape aand the cross-sectional shape b. By generating a tumble flow having thespeed (flow speed) according to the perimeter La(x, θ) in this manner, atumble flow having a uniform circulation time and a uniform circulationaxis, that is, a good tumble flow, can be generated.

FIG. 4 is a schematic cross-sectional view of the intake pipe 60.Specifically, FIG. 4 illustrates the cross-sectional shape of the intakepipe 60 taken in a cross section (first cross section) orthogonal to thedirection in which the intake passage 36 of the intake pipe 60 extends.In FIG. 4, the intake pipe 60 has a rounded-corner rectangularcross-sectional shape for simplifying the description of the shape ofthe intake pipe 60. In this example, the cross-sectional shape of theintake pipe 60 varies in the direction in which the intake passage 36 ofthe intake pipe 60 extends. In FIG. 4, the longitudinal direction of theintake pipe 60 having the rounded-corner rectangular shape is defined as“Y direction”.

Since the intake air flows along the intake pipe 60 before entering thecombustion chamber 22, the shape of the intake pipe 60 also has aneffect on the generation of a good tumble flow. For instance, in a casewhere the first intake passage 36 a is closed by the TGV 50, asdescribed above, intake-air flow-speed distribution according to thecross-sectional shape of the second intake passage 36 b, that is, theshape of the surface where the intake pipe 60 and the partition plate 48face each other, is formed within the second intake passage 36 b. Theintake-air flow-speed distribution according to the shape of the surfacewhere the intake pipe 60 and the partition plate 48 face each other isreflected on a tumble flow to be generated within the combustion chamber22. Therefore, in order to generate a good tumble flow, it is alsonecessary to consider the shape of the surface of the intake pipe 60that faces the partition plate 48.

Accordingly, in order to realize a good tumble flow, it is necessary toset the shape of the partition plate 48 based on the shape of thecombustion chamber 22 (i.e., the aforementioned perimeter La(x, θ) ofthe combustion chamber 22) and the shape of the intake pipe 60 (i.e.,the aforementioned shape of the surface of the intake pipe 60 that facesthe partition plate 48).

In detail, the shape of an opposing surface of the partition plate 48facing the intake pipe 60 with the second intake passage 36 b interposedtherebetween in a cross section orthogonal to the extending direction ofthe intake pipe 60, that is, a shape Lb(Yp, l) of the partition plate48, is calculated (set) in accordance with expression (4) indicatedbelow. In expression (4) indicated below, the shape Lb(Yp, l) expressesthe distance from an opposing surface (i.e., the inner bottom surface)of the intake pipe 60 facing the partition plate 48 with the secondintake passage 36 b interposed therebetween to the opposing surface ofthe partition plate 48 facing the intake pipe 60 with the second intakepassage 36 b interposed therebetween.Lb(Yp,l)=Ip(Yp,l)+a·La(x,θ)+b  (4)

In this case, Ip(Yp, l) denotes a shape 60 b of the opposing surface(i.e., the inner bottom surface) of the intake pipe 60 facing thepartition plate 48 with the second intake passage 36 b interposedtherebetween, a denotes a coefficient set based on, for instance, atumble ratio and the shape of the intake valve 32, b denotes acoefficient for setting the opening area of the second intake passage 36b, Yp denotes any position in the longitudinal direction of thepartition plate 48 (or the intake pipe 60) in the cross sectionorthogonal to the extending direction of the intake pipe 60 (simplyreferred to as “extending direction” hereinafter), l denotes anyposition in the extending direction, and θ denotes a crank angle of theengine 1. The coefficients a and b are values (coefficients) determinedfrom an empirical formula.

FIG. 5 is a schematic cross-sectional view of the intake pipe 60 and thepartition plate 48. In FIG. 5, the shape Lb(Yp, l) of the partitionplate 48 calculated from expression (4) is illustrated. As illustratedin FIG. 5, the partition plate 48 has a curved shape in the crosssection orthogonal to the extending direction.

It is apparent from expression (4) that the shape Lb(Yp, l) of thepartition plate 48 is set based on the perimeter La(x, θ) of thecombustion chamber 22 and the shape 60 b (Ip(Yp, l)) of the intake pipe60.

By setting the shape Lb(Yp, l) of the partition plate 48 based on theshape 60 b (Ip(Yp, l)) of the intake pipe 60, the distance between theintake pipe 60 (i.e., the shape 60 b) and the partition plate 48 can befixed, so that the flow-speed distribution of intake air flowing withinthe second intake passage 36 b can be made uniform in the Y direction.

Furthermore, by setting the shape Lb(Yp, l) of the partition plate 48based on the perimeter La(x, θ) of the combustion chamber 22, a tumbleflow having a speed (flow speed) according to each perimeter La(x, θ) inthe x direction of the combustion chamber 22 can be generated, whereby agood tumble flow having a uniform circulation time and a uniformcirculation axis can be generated within the combustion chamber 22.

Therefore, according to this example, the shape Lb(Yp, l) of thepartition plate 48 that satisfies expression (4) is set, so that apartition plate 48 that can effectively generate a tumble flow and thatcan improve the combustion stability of the engine 1 can be provided.

Modification

In the above description, the shape Lb(Yp, l) of the partition plate 48is calculated assuming that the intake air flows (i.e., a tumble flow isgenerated) along the wall surface of the combustion chamber 22. However,in actuality, the intake air does not always flow along the wall surfaceof the combustion chamber 22, such that a tumble flow may sometimes begenerated away from the wall surface of the combustion chamber 22.

In this modification, the shape Lb(Yp, l) of the partition plate 48 iscalculated (set) assuming that a tumble flow is generated away from thewall surface of the combustion chamber 22.

In that case, a good tumble flow having a uniform circulation time and auniform circulation axis can be generated by causing the tumble flowgenerated within the planes of the cross-sectional shapes a and b inFIGS. 2B and 2C to have the same speed.

In detail, the shape Lb(Yp, l) of the partition plate 48 is calculated(set) in accordance with expression (5) indicated below.Lb(Yp,l)=Ip(Yp,l)+b  (5)

FIG. 6 is a schematic cross-sectional view of the intake pipe 60 and thepartition plate 48 according to this modification. In FIG. 6, the shapeLb(Yp, l) of the partition plate 48 calculated from expression (5) isillustrated. As illustrated in FIG. 6, the partition plate 48 has acurved shape in the cross section orthogonal to the extending directionof the intake pipe 60.

It is apparent from expression (5) that the shape Lb(Yp, l) of thepartition plate 48 is set based on the shape 60 b (Ip(Yp, l)) of thesurface of the intake pipe 60 that faces the partition plate 48 in thesecond intake passage 36 b.

By setting the shape Lb(Yp, l) of the partition plate 48 based on theshape 60 b (Ip(Yp, l)) of intake pipe 60, the distance between theintake pipe 60 (i.e., the shape 60 b) and the partition plate 48 can befixed, so that the flow-speed distribution of intake air flowing withinthe second intake passage 36 b can be made uniform in the Y direction.

Accordingly, by setting the shape Lb(Yp, l) of the partition plate 48that satisfies expression (5), the speed of the tumble flow in the y-zcross section of the combustion chamber 22 can be made the same, wherebya good tumble flow having a uniform circulation time and a uniformcirculation axis can be generated.

Therefore, according to this modification, the shape Lb(Yp, l) of thepartition plate 48 that satisfies expression (5) is set, so that apartition plate 48 that can effectively generate a tumble flow and thatcan improve the combustion stability of the engine 1 can be provided.

Although a preferred example of the present invention has been describedabove with reference to the appended drawings, the present invention isnot limited to the example. It is apparent to a skilled person thatvarious modifications and alterations are conceivable within thetechnical scope described in the claims, and it is to be understood thatsuch modifications and alterations belong to the technical scope of thepresent invention.

For instance, the partition plate 48 may be given an intermediate shapebetween FIGS. 5 and 6 by performing an interpolation process on theshapes of the partition plate 48 in FIGS. 5 and 6.

The above description corresponds to a case where the first intakepassage 36 a is closed. Alternatively, the second intake passage 36 bmay be closed such that a tumble flow may be generated by intake airtraveling through the first intake passage 36 a. In that case, the shapeLb(Yp, l) of the partition plate 48 is set based on a shape 60 a of thesurface of the intake pipe 60 that faces the partition plate 48 with thefirst intake passage 36 a interposed therebetween.

According to the example of the present invention, a partition platethat can effectively generate a tumble flow and that can improve thecombustion stability of the engine can be provided.

The invention claimed is:
 1. A partition plate configured to separate anintake passage formed by an intake pipe to be coupled to a combustionchamber into a first intake passage and a second intake passage, thefirst intake passage being openable and closable by a tumble generationvalve, the partition plate and the tumble generation valve disposedbetween an intake valve and the combustion chamber, comprising: a shapeof a first cross section of the partition plate orthogonal to anextending direction of the intake pipe is set on a basis of a shape of abottom surface of the intake pipe that faces the partition plate withthe second intake passage interposed therebetween, the second intakepassage being smaller in cross section than the first intake passage,and wherein a distance between a central part of the partition plate ina width direction and the bottom surface is equal to or longer than adistance between ends of the partition plate in the width direction andthe bottom surface, wherein the shape of the first cross section is seton a basis of a shape of the combustion chamber, wherein the shape ofthe first cross section satisfies an expression Lb(Yp, I)=Ip(Yp,I)+a*La(x, θ)+b; where Lb(Yp, I) denotes the shape of the first crosssection, Ip(Yp, I) denotes the shape of the surface of the intake pipethat faces the partition plate with the second intake passage interposedtherebetween, La(x, θ) denotes a length in a circumferential directionalong a wall surface of the combustion chamber in a second cross sectionincluding a first direction corresponding to an axial direction of acylinder bore of an ermine and a second direction extending from anintake side toward an exhaust side of the combustion chamber, a denotesa coefficient set based on a tumble ratio and a shape of the intakevalve, b denotes a coefficient for setting an opening area of the secondintake passage, Yp denotes any position in a longitudinal direction inthe first cross section, I denotes any position in the extendingdirection, and θ denotes a crank angle of the engine.
 2. The partitionplate according to claim 1, wherein the shape of the first cross sectionis set on a basis of a length in a circumferential direction along awall surface of the combustion chamber in a second cross sectionincluding a first direction corresponding to an axial direction of acylinder bore of an engine and a second direction extending from anintake side toward an exhaust side of the combustion chamber.